1. Field of the Invention
The invention generally relates to highway structures and more specifically to a safety roadway delineator which is substantially immune from normal wear and reliably exhibits reflectivity both under dry and rainy night-time weather conditions and method of making the same.
2. Description of the Prior Art
Reflective stripes and other markings have been provided on highways and highway structures, such as curbs and median barriers, in order to delineate or identify the boundaries of a highway or to divide lanes on a multi-lane highway. One of the major problems with such delineators has been their visibility under different driving or weather conditions, on the one hand, and the durability of such markings or stripes, on the other hand.
While such delineators function properly and efficiently under ideal driving or weather conditions, their usefulness frequently deteriorates during inclement weather, particularly when it rains. Under such adverse conditions, the delineators are frequently not clearly visible and this poses a danger or hazard to those using the highway or road. The problem and the need for a solution have been discussed by transportation engineers and others who are involved with the design, construction and maintenance of highways. See, for example, "ITE Hearing Record--Performance Standards For Retroreflectivity Of Traffic Control Devices", Institute of Transportation Engineers, Aug. 21, 1985; and "Operation, Safety and Maintenance Of Transportation Facilities", Transportation Research Circular No. 306, June, 1986, Transportation Research Board, National Research Council. In the foregoing publications, there is discussed the need to improve markings for highways, particularly under wet or rainy night-time driving conditions.
With the introduction of relatively durable paints and applied plastics, along with the advent of retroreflective glass microspheres, a partial solution to night-time traffic delineation has become available. However, these techniques still have certain drawbacks. For example, reflective markers or delineators which are exposed to normal traffic will wear down or be adversely effected by inclement weather, road salt and corrosive and chemical attack, and mechanical snow removal equipment. Additionally, during wet or rainy weather driving conditions, water causes the refractive and reflective light indices to change for both reflective beads and the base materials. In some cases, the wetting of such reflective materials cause the total visual disappearance of the demarcation elements. Such visual deviation is due to a "mirror" effect of the headlights impinging upon the water on the reflective material instead of directly on the reflective material itself. All of these disadvantages are true not only of roadways, but also curbs, median dividers, and other traffic routing devices.
Numerous solutions have been proposed for achieving the goal of providing a reliable highway delineator which functions satisfactorily both during ideal as well as during inclement weather conditions. For example, in U.S. Pat. No. 2,345,644, issued to Weber on Apr. 4, 1944, there is described a light reflecting sign or marker which utilizes a Portland cement base poured on site and relatively large glass reflective beads are imbedded in a pre-cast panel of white Portland cement which is imbedded in the cement curb. However, the panel is disposed at the exterior surface of the cement base which is exposed to the vehicular traffic. The glass beads, in fact, project beyond the surface and, therefore, are susceptible to contact with vehicles and, therefore, the probability that such glass reflective beads will be dislodged is substantial.
In U.S. Pat. No. 3,203,327, issued to Daley on Aug. 31, 1965, a cast metal street curb is disclosed which includes vertical ribs or recesses. Although the patentee does not show reflective material within such recesses, he does mention that it is possible to provide paint or a similar finish in order to enhance the visibility of the curb to motorists at night. However, Daley does not teach or suggest the use of elongate horizontal delineators which run generally parallel to the road and which are recessed and provided with retroreflective materials in order to enhance the amount of reflection under adverse weather conditions.
U.S. Pat. No. 4,000,882, issued to Penton on Jan. 4, 1977, discloses a contrasting marker panel for highway guardrails. Penton intends, however, to utilize his invention with the most commonly used form of continuous guardrail which is formed of sheet iron or steel. Penton utilizes a marker panel which is receivable within the trough of the guardrail and covered with a plastic film. Penton suggests that such plastic film may sometimes be reflectorized and also suggests that a reflector or reflectors may, in certain instances, be mounted within the trough so as to be exposed outwardly of the guardrail recess.
The Penton marker panel is not, how ever, suitable for use in connection with other highway safety structures, particularly those made of cast-in-place concrete or pre-cast elements.